Seven facts about illegal immigrants in the United States

A line of legal immigrants wait outside the Coalition for Humane Immigrant Rights in Los Angeles offices Wednesday, Aug. 15, 2012. Hundreds of thousands of young illegal immigrants scrambled to get papers in order, as the U.S. started accepting applications to allow them to avoid deportation and get a work permit, but not a path to citizenship. President Barack Obama announced the program in June after pressure from Hispanic voters and others who said he hasn't fulfilled a campaign promise to overhaul tangled U.S. immigration laws. (AP Photo/Nick Ut)

Seven facts about illegal immigrants in the United States

Congress will debate a massive overhaul of the immigration system this year. At the center of Democratic proposals will be a pathway to citizenship for illegal immigrants.

Here’s seven facts you need to know about illegal immigrants in the United States.

There are about 11 million illegal immigrants in the U.S.

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Araceli Cortes, an illegal immigrant, is shown at her home in California in 2012. (AP Photo/Reed Saxon)

No one knows exactly how many illegal immigrants live in the United States. In its most recent report, the Department of Homeland Security estimated there were 11.5 million in January 2011.

Most are between the ages of 25 and 44.

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People fill the hall of a New York Church for a workshop on deferred action for illegal immigrants in 2012. (AP Photo/Richard Drew)

According to Department of Homeland Security estimates, 26 percent are below the age of 24, 59 percent are between 25 and 44 and 15 percent are over the age of 44.

Most — but not all — illegal immigrants are from Mexico.

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Lizbet Galvan, from Mexico, left, talks to a paralegal about getting her deportation deferred in 2012.(AP Photo/Damian Dovarganes)

That same report estimates that 59 percent of illegal immigrants are from Mexico. Other countries in the top 10: El Salvador, Guatemala, Honduras, China, the Philippines, India, Korea, Ecuador and Vietnam.

There are only slightly more men than women.

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Sonia Limas, an illegal immigrant, talks with a reporter at her home in Texas in 2012. (AP Photo/Eric Gay)

Contrary to popular perception, there are a large number of female illegal immigrants. The Department of Homeland Security estimates that 53 percent are men and 47 percent are women.

Most illegal immigrants live in a handful of states.

More than three-fourths of illegal immigrants live in a dozen states, mostly larger states such as California, Texas, Florida, New York and Illinois. However, illegal immigrants live in every state.

They tend to work in farming, maintenance and construction.

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Pedro Leon smiles while filing out paperwork to get a workers permit in 2012. (AP Photo/Grant Hindsley)

According to the Pew Hispanic Center, occupations with high shares of illegal immigrants include farming (25 percent), building maintenance (19 percent), construction (17 percent) and food preparation and serving (12 percent).

Illegal immigration appears to have peaked in 2007.

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Itzel Guillen, left, sorts documents she needs for a work permit under a deferred action program in 2012. (AP Photo/Gregory Bull)

The Pew Hispanic Center estimates that the number of illegal immigrants in the United States peaked in 2007 at 12 million before dropping to around 11.1 million in 2009 and remaining level since, likely due to the poor economy.